Aluminum-base alloys

ABSTRACT

AN ALUMINIUM BASE ALLOY IS DISCLOSED WHICH CONTAINS GERMANIUM, MAGNESIUM AND COPPER. PREFERABLY, THE ALLOY COMPRISES 0.02% TO 0.25% GERMANIUM, 0.1% TO 0.5% MAGNESIUM, AND 4.0% TO 6.5% COPPER, WITH IF DESIRED UP TO 0.5% SILICON, UP TO 1% MANGANESE AND UP TO 0.5% IRON.

Feb. 9, 19'71A G. B. BROOK ALUMINUM-BASE ALLOYS Filed Feb.- 19, 1968 2- Sheets-Sheet 1 1 Om INP IQ IN E@ EON 2o Wow mvo m mvo 1| N m O|j looP m5 m I m g m o m oj Smm .Z cw 5mm 5mi o :o l.

#4+ t ou 1T +4. l M+ rt.: o 0W+ KMO o+l+\.+ .loi /O om@ Oo C lomo v Y 'N'J'U SSEINUHVH Feb- 9, 1971 G. a. BROOK ALUMINUM-'BASE ALLOYS 2 Sheets-Sheet 2 Filed Feb. 19, 1968 ma il :azi :Ea :Q s@ z ma@ .NGE Z mi: z QQ Q E E Y 5.o a Ow, ,I Q f N. z? N .M29 x K Y POE l 0V Xl-IIX 0 oo\fx\x\x\m .No. 0\ xx ++\+|l+ A OMS v -QQ X l -es A -sf Ax 2.@ a@ @mx .s l o -QQ a @QS l $8 .smi $5 nited States Patent C) U.S. Cl. 75-142 14 Claims ABSTRACT .0F THE DISCLOSURE An aluminium base alloy is disclosed which contains germanium, magnesium and copper. Preferably, the alloy comprises 002% to 0.25% germanium, 0.1% to 0.5% magnesium, and y4.0% to 6.5% copper, with if desired up to 0.5% silicon, up to 1% manganese and up to 0.5% iron.

This invention relates to aluminium-base alloys containing a strengthening element such as copper as a major alloying constituent, especially aluminium-base alloys containing magnesium in addition.

Aluminium-base alloys containing a strengthening alloying element such as copper as a major alloying constituent, and both copper and magnesium as major alloying constituents, are used extensively because of their desirable mechanical and physical properties and ease of manufacture. Recently they have found increasing use as Creep-resistant materials.

Such alloys respond to heat treatment at high temperatures of 450 to 550 C. depending on composition (usually called solution treatment), followed by rapid cooling to temperatures below 2.5a C. after which the alloys may be aged either at room temperature (natural ageing) or at elevated temperature (artificial ageing) to increase their strength. Artificial ageing produces more rapid hardening and enables the maximum strength to be attained. It may he necessary to deform the alloy, e.-g. for convenience in manufacture or to assist hardening, vand this is preferably carried out as soon as possible after rapid cooling following solution treatment and before the maximum hardness is reached.

We have found .that small additions lof germanium up to 0.5% have beneficial effects on such aluminium lalloys.

The present invention provides an aluminum lbase alloy which consists essentially of 0.2% to 0.5% germanium, 0.1% to A0.5% magnesium, 2% to 7% copper and the balance essentially aluminum.

The preferred amount .of germanium is 0.2% to 0.4%, and more `particularly 0.02% to 0.25%. The preferred amount of copper is 4.0% to 6.5% Preferably any silicon present does not exceed `0.5% any manganese present does not exceed 1% and any ironl present does not exceed 0.5 The alloys of the present invention may thus contain other elements, whether as impurities or as additions for modifying certain properties, provided that the impuritiesvor additions are not such as to prevent fthe attainment of the beneficial effects described herein. For example, silicon may be present in an amount up to 0.1% for alloys where avoidance-of room temperature aging is required, or in excess of 0.1% where easy fabrication is not of great importance, but resistance to .creep following artificial aging is required. Any of the known precipitate or grain reners may be added to the alloys of the present invention, lfor example, silver, titanium, chromium, vanadium or zirconium, for the purpose of modifying grain size or their effect on recrystallization behavior. For certain applications, particularly those involving resistance to high temperature, it may be desirable to add up to 2.5% nickel and 1.5% iron.

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The aforesaid beneficial effects are (i) that the rate of hardening and maximum hardness attained on natural ageing are very much reduced so that it is not necessary to carry out operations involving deformation immediately after quenching from solution treatment; (ii) that the rate of hardening to maximum hardness and maximum mechanical properties on artificial ageing is considerably higher than in alloysfree from magnesium or germanium7 or containing either magnesium ,or germanium alone; and (iii) that the resistance to overageing at elevated temperatures especially during creep is better than in comparable alloys without magnesium plus germanium.

Our experiments have shown that 'magnesium plus germanium additions -nucleate the O `precipitate of the aluminium-copper-system more effectively than other `trace elements such as cadmium, indium and tin, in aluminium alloys containing from 2 to 7% copper, or than magnesium and silicon together in the Well-known alloy containing typically 5-6% Cu, 0.3% Mg, 0.15% Si and 0.25% Mn, and that this is believed to be the reason for the aforesaid beneficial effects.

vBy way of example, and to illustrate the invention, we have compared the properties of two aluminium-base alloys containing copper as a major alloying constituent, namely a well-known one containing also magnesium and silicon, and one according to the invention and containing also magesium and germanium. These alloys are hereinafter identified as Alloy A and Alloy B, respectively, and Alloy A contains 5% copper, 0.2% magnesium, 0.15 silicon, 0.5 manganese and 0.15% iron; and Alloy B contains 5% copper, 0.2% magnesium, 0.5 germanium, 0.5% manganese and 0.15% iron.

Forged bars of both alloys were solution treated at 530 C. quenched into cold water and were then aged at C. Alloy A reached the maximum mechanical properties after ageing for 24 hours, whereas Alloy B hardened more rapidly reaching its maximum in 91/2 hours.

Time 0.1% proof Elongation at 170 C., stress, Max stress, percent 0E Alloy hours tons.t./in.2 tons../in.2 4 1/A C The effect of the magnesium, plus germanium additions, was more lmarked at higher ageing temperatures, c g. at 190 C.

into lwater and aged at ambient temperature for 14 days. Alloy A increased in hardness from 83 D.P.N. to 92 D.P.N. whereas the hardness of Alloy B remained constant at 81 D.P.N. After 23 days the hardness of Alloy A had risen to 116, and Alloy B to 99 D.P.N.

The lower rate of hardening of the alloy containing magnesium, plus germanium, is also shown by measureo ments of mechanical properties of forged bars solution treated at 530 C., quenched in Coldwater, and aged for 32 days at ambient temperature.

The superiority of Alloy B with germanium in creep is also shown in the higher strength retained after prolonged exposure at 150 C.

Tensile properties As aged Alter 100 hrs. at 150 C. After 1,000 hrs. at 150 C.

117 Elonga- 0.117 Elonlga- 0.117 Elongaprooi Maxnon proof Max. 'non prooi7 Max tum stress, stress, pmi@ stress, stress, 9810.31.12 stress, Stress. pelceni" Alloy Heat treatment t.s.i t.s.i onu/A t.s.i.v t.s.1. ouh/A t.s.i t.si.' ouh/A 24 hours at 1707 20. 3 28. 4 17 21. 3 28.7 14 19. 1 27.9 13 A As silicon is a naturally occurring impurity in alumi- Time at El .t num, we have also examined alloys of the invention conambient 01% Proof gifelolr; taining different amounts of silicon, together with variatemperature, stress, Max. stress, p Ahoy days u51. /ing 10mm/iu; NIA tions 1n magnesium and germamum content.

. 32 14 o 26 4 l 30 20 In s1l1con-free alloys we have found only little ad- 32 917 2216 29 vantage in ageing characteristics or in mechanical prop- Thus Alloy B containing germanium with magnesium not only has higher mechanical properties attained in a shorter ageing time at 170 C. or 190 C. but ages more slowly at room temperature after solution treatment.

Ageing curves for Alloys A and B at 165 C. are also shown in FIG. 1. Similar effects are shown with somewhat lower copper contents and with alloys made from high purity aluminum. FIG. 2 shows the hardness ageing erties in adding more than 0.2% germanium. The presence of silicon does not interfere with the effect of the combined magnesium plus germanium additions. Even in the presence of silicon, as little as 0.02% germanium causes a significant improvement in maximum strength and,y as in silicon-free alloys, there is only little advantage in adding more than about `0.2% germanium.

This is-illustrated in the properties of the following alloys, forged bars of which were quenched from 530 C.

into cold water and were aged at 170 C. for the times shown:

curves at 165 C, for alloys containing approximately 4.0% copper and with additions of magnesium or germanium or magnesium plus germanium. It is manifest that magnesium or germanium additions by themselves are markedly less effective than combined additions of magnesium and germanium, the latter producing both accelerated and enhanced age-hardening at this temperature.

Alloy B also shows more resistance to creep at temperatures in the region of 150 C. Forged bars of Alloy A and Alloy B 'were quenched from 530 C. into water and aged 24 hours and 116 hours respectively at 170 C. They A comparison of Alloys C, D and E shows that the presence of silicon does not interfere with the beneficial effect of magnesium plus germanium. A comparison of Alloys F and G shows that the only effect of further additions of germanium is further acceleration of hardening without any major increases. f f

Higher strengths can be achieved by incseasing the copper content of the alloy, e.g. with 6% copper, 0.1%

proof stresses, over 30 tons.f./in.2 can be obtained, as can be seen from a comparison of Alloys H, l and I. As before, forged bars were quenched into coldfwater from 530 C. and aged at 170 C.:

. Ageing 0 1% Elonga- Composltlon, percent time at proof Max tion 170 C., stress, stress, percent Alloy Cu Mg Si Ge Mn Fe hours t.s.i t.s.1 onl/ H 4.98 0.28 0.02 0.40 0.53 0.27 8 lg 1 5.50 0.27 0.02 0.37 0.50 0.25 15 J 5.95 0.29 0.02 0.39 0.53 0.20 10 were then subjected to creep at 150 C. under a stress of l2 tons.f./in.2, with the following results:

.Percent plastic strain Alloy after 1000 hours A 0.110

One effect of silicon is to increase the amount of hardening occurring at ambient temperature after quenching from solution treatment. Whilst this is undesirable if the material is to be formed before ageing aty higher temperatures, there are circumstances when such hardening B 0.045 is desirable, e.g. after welding solution treated and aged material, when some strengthening of the re-solution treated and quenching zone is required without subsequent articial ageing of the whole structure.

Typical properties for forged bars of Alloys C, D, E, F, G and H after solution treatment at 530 C. quenching in water and ageing at ambient temperature for 21 days are given below:

A comparison between Alloys E and F shows that as little as 0.1% silcon, plus 0.1% magnesium, will cause some hardening at ambient temperatures, even in the presence of 0.2% germanium.

The alloys according to the invention, when intended for fabrication or welding, are solution treated at 530 C. and quenched in water before the fabrication or welding. For applications requiring maximum mechanical properties, the alloys may be aged at temperatures in the range 150 C. to 2110" C. following the solution treatment.

I claim:

1. An aluminum base alloy consisting essentially of 0.02% to 0.5% germanium, 0.1% to 0.5% magnesium, 2% to 7% copper and the balance essentially aluminum.

2. An aluminum base alloy according to claim 1, containing 0.02% to 0.4% germanium.

3. An aluminum base alloy according to claim 1, containing 0.02% to 0.25% germanium.

4. An aluminum base alloy according to claim 1, containing 4.0% to 6.5% copper.

5. A11 aluminum base alloy according to claim 1, containing at least one element selected from the group consisting of silicon, Imanganese and iron in an amount up to 0.5 1% and 0.5 respectively.

6. An aluminum base alloy according to claim 1, containing nickel in an amount up to 2.5% and iron in an amount up to 1.5%.

7. An aluminum base alloy according to claim 1, containing silicon in an amount up to 0.1%

8. An aluminum base alloy according to claim 1, containing silicon in an amount in excess of 0.1% and up to 0.5

9. A11 aluminum base alloy consisting essentially of 0.02% to 0.4% germanium, 0.1% to 0.5% magnesium, 4.0% to 6.5% copper and the balance essentially aluminum.

10. An aluminum base alloy according to claim 9, con taining 0.02% to 0.25% germanium.

11. An aluminum base alloy according to claim 9, containing at least one element selected from the group consisting of silicon, manganese and iron in an amount up to 0.5 1% and 0.5 respectively.

12. An aluminum base alloy according to claim 9, containing nickel in an amount up ot 2.5% and iron in an amount up to 1.5%.

13. An aluminum base alloy according to claim 9, containing silicon in an amount up to 0.1%.

14. An aluminum base alloy according to claim 9, containing silicon in an amount in excess of 0.1% and up to 0.5

References Cited UNITED STATES PATENTS 3,346,374 10/1967 Jagaciak 75--147 FOREIGN PATENTS 484,395 10/1929 Germany.

OTHER REFERENCES 'Chemical Abstracts, Fridlyander et al., July 9, 1962, vol. 57. No. 1, pp. 544i-545a.

O 'RICHARD O. DEAN, Primary Examiner U.S. Cl. X.R. 14S- 32.5, 159 

